This invention relates to a photographic camera provided with flash means, and more particularly, to a camera of the above-described type in which a predetermined voltage level for discharging an electronic flash is indirectly confirmed by checking whether the level of the power source voltage has recovered to a predetermined stable level or not, and, if not, initial actuation for taking photographic pictures with a camera of the above-described type cannot be brought about.
With respect to a circuit arrangement of the camera provided with flash means for taking photographic pictures with the help of flash light, it is mandatory prior to taking a photograph to check whether the charging of the main capacitor of the flash means has been completed or not because firing of the flash means when the main capacitor is insufficiently charged results in a photograph with insufficient illumination of the photographed object. To this end, there have conveniently been proposed various arrangements for warning of an insufficient charge on the main capacitor or prohibiting an initial actuation of the shutter release of the camera until the completion of the charging of the main capacitor.
A popular arrangement for the above described checking of the state of the charge on the main capacitor is one which checks the voltage across the main capacitor, which is to be raised to a high level by a voltage boosting circuit, or a voltage obtained by dividing the main capacitor voltage by way of a bleeder circuit, as is disclosed, for example, in Japanese Laid Open Patent Application Tokkaisho No. 49-5618(1974). However, this arrangement suffers from the drawback that circuit elements which can withstand a high voltage are required because the voltage to be detected is a high voltage as mentioned above.
An arrangement which can obviate this drawback is disclosed in Japanese Utility Model Publication No. 49-23869(1974), for example. This arrangement makes use of the fact that, in the course of the procedure for charging the main capacitor by way of an electric power source and a voltage boosting circuit of the oscillating type, the power source voltage is first abruptly lowered to quite a low level and then gradually returned to the stable rated level thereof. That is to say, a voltage checker means or a checker means which checks the power source voltage is provided in this arrangement for the checking on the state of the charge on the main capacitor.
However, the voltage recovery characteristic from the low level to the constant stable level described above is commonly accompanied by a certain amount of voltage fluctuation around the time-averaged instant value thereof, due to the effect of incorporation of the voltage boosting circuit in the power source circuit so as to boost the voltage, to obtain the high voltage level for charging the capacitor as described above. Therefore, a voltage checker means or a checking means for checking the level of the power source voltage, which is generally incorporated in the circuit arrangement for the camera of the above-described type, sometimes produces a signal indicating the full recovery of the voltage level of the power source voltage corresponding to the completion of electric charging of the capacitor, and thus indicating the possibility of starting actuation of the camera for taking photographic pictures with resultant faulty pictures, because the level of the power source has only apparently been brought up to the predetermined power rating by a positive instant fluctuational peak in the time-averaged power voltage which is recovering to the above-mentioned rating.